cutting things out square

[james butler]

a friend of mine needs a new spare wheel well welding into his car and has a new wheel well thats been cut from a rust free car.
in order to weld in into his car how would you guys n gels measure and cut the old one out squarely so the new one butt joints in nicely?
its not the easiest shape to mark out or measure from so I'm a bit worried of cutting both out and then having huge gaps i will have to weld up.

james

 

[Mee]

Usually I cut them out after taking a picture or two and putting alignment marks onto them to act as rough datum points.

 

[james butler]

hmm i kinda see what you mean but knowing me if i don't mark it out on both pieces exact it will come out really cockeyed
i could really do with one of those 360 degree laser level things as that would give a perfect straight line

 

[colnerov]

Hi, Cut round the old wheel well just where it starts to curve down into the well, drop the new panel into the hole and it will automatically centralise it, turn it round until it's in the right orientation, then scribe round the outside. Remove the new panel, trim back the boot floor to the scribed mark, then weld in the new panel. If you're butt welding and dressing back it doesn't matter if the cuts are not perfectly straight because you won't see them afterwards.

Colin

 

[anjum]

One idea might be to drill a small hole, if there's not a suitable fixing point already, in the centre of the bottom of the wheel well and then get a fixed length of string or wire. Use that to mark as many places around the edge of the well as possible then use the same on the replacement panel. Try it by holding the end in the center first to get the best location for the hole and the best length of string/ wire. Drill the hole in the same place in the replacement panel and mark, the marks should be in the same places as the the original. Remember measure twice, cut once!
Join the dots on both panels and hopefully you'll get a match.
Caveat -never tried this myself but it seems to make sense to me.

Or you could use an overlap weld using a joggler or is that swearing on here??!!

 

[Wallace]

Are there rubber bungs in the wheel well? If so, the holes are used to line panels up on a jig in the factory for welding and a makeshift jig can be fixed in place to align the new panel of the fit is critical.

 

[steveo3002]

what if you cut each one near enough ...plonk the new panel into the hole and screw down in a few spots , then use a 1mm cutter disc to cut through both parts ?

put a few tacks as you go ?

 

[optima21]

there are a few different ways to do it. if you have the edge of the floor on the donor wheel well, and it is spot welded to the wheel well. you could remove the spot welds so that just leaves the wheel well. then cut most of the rotten wheel well out and then remove the spot weld from the edge leaving an intact boot floor. you could drill one of the sets of spot welds out and leave holes so you can plug weld the donor wheel well into the boot floor. just drop the wheel well into the hole in the boot floor and weld it up.

it also depends on how much time you have to spend doing it and what you want the finished repair to look like.

if its only a few small areas that need replacing, it might be easier just to replace those sections

 

[bigegg]

Make a cardboard template?
Or several, until you get one thats perfect.

 

[Robotstar5]

Place new wheel well on a piece of cardboard, draw round it, cut to drawn line, turn it over and mark round template to give cut line on rusted well.

 

[Paul G]

Is that a square wheel well, or a spare square wheel well, or a square spare wheel well ?

I'm getting confused.

 

[james butler]

here is the wheel well as it is,
i think cutting the old one squarish then drop the new one in and scribe around the out side like colnerov said seems the easiest idea but thanks to everyone who's replied theres some great ideas

 

[james butler]

as you can see it was pretty bad. its a saab aero and not a critical area to weld up but would like to do a reasonably good job. i suppose once seem sealed over it won't look too bad

 

[james butler]

heres the inside of the front wheel arch
gonna be busy

 

[optima21]

here is the wheel well as it is,
i think cutting the old one squarish then drop the new one in and scribe around the out side like colnerov said seems the easiest idea but thanks to everyone who's replied theres some great ideas

looking at the shape of it (and the taper of it), I'd go for that too. just wondering if you can plug weld the donor section in place rather than seam welding as its not likely to be in a prescribed area for MOT's.

 

[marlinspike]

A good way to make a template is to use masking tape. You lay it in overlapping strips across the hole or shape, then use a pencil to press on the tape and mark the edge. This gives a very accurate template if you do it carefully. Cut out the shape and place on your new metal.

It works well for tricky shapes in difficult areas. Our old Saab 900 had a rotten inner wheel arch. Having cut the rotten bit out we needed to have an accurate template for the gap between the good metal and the new wing as we were using a replacement panel. By using the masking tape in horizontal strips we got a good pattern and the new metal was a tight fit: